This invention relates generally to movements of hovering vehicles, and more specifically, to methods and systems for maintaining a position during hovering operations.
Typical helicopter and other hovering vehicle maneuvers include maintaining a hover position defined by vertical and horizontal components. Maintaining a hover position is sometimes referred to as a hover hold. One specific example of a hover hold scenario is during rescue operations. It is of great benefit to the pilot, especially during turbulent or high wind conditions, to have an automatic hover hold system wherein motion is sensed and automatically corrected to provide average zero horizontal and vertical velocities. Because motion sensing with respect to the ground typically is desired, a radar velocimeter system is typically utilized in an automatic hover hold system. Known radar velocimeter systems typically utilize at least three narrow beam directional antennas providing directional Doppler ground velocity sensing. These narrow beam antennas are rather large in size as compared to, for example, an antenna for a radar altimeter.
In addition to the radar velocimeter system, a radar altimeter is typically used to determine altitude with respect to the ground. Known radar altimeters which operate in the altitude range associated with hover hold operations utilize both transmit and receive antennas. While effective, the two separate systems (radar velocimeter and radar altimeter) are costly, and the five antennas employed by such systems utilize a great deal of the surface area of the vehicle, lessening space available for installation of other systems. In addition, weight considerations of the two separate systems are also a potential problem to be considered.